The correct setting of the boiling power for cooking (potatoes, noodles, vegetables, eggs and, if desired, also meat) requires constant supervision by the user. In most cases the heating power is then increased or reduced by hand in the usual manner, depending on whether the substance to be cooked simmers. In order to guarantee steady boiling the power is then often set to a value larger than the power actually required for the process. This means an increased power consumption, an increased steam production, more cooking odors, and sometimes spoiling of the food being cooked.
DE-GM 81 31 827 discloses a device for the heat treatment of foodstuffs, in particular for the preparation of meals, by means of a steam-air mixture as a heat-transfer medium. A motor-driven fan then circulates the steam-air mixture at atmospheric pressure in a cooking space which can be closed by means of a door. The cooking space is provided with a controllable moisture exhaust and with a condensate outlet. Moreover, there is provided a heating device for the heat-transfer medium and a special steam generator with a temperature-controlled heating element. An associated temperature controller comprises a sensor arranged in a connection from the cooking space to the surrounding air, through which the steam-air mixture can emerge only after overcoming its net lift. In the known construction the sensor is situated inside a tube underneath the bottom plate of the cooking space. The tube serves for discharging the condensate and as a measurement-sensor tube. The known device has a special steam generator for the delivery of steam to the separate cooking space. The amount of steam to be generated and to be introduced in a uniformly distributed manner should be only so much as needed for the acceleration of the defrosting or cooking process by the transfer of condensation heat to the foodstuffs and meals. Excess steam will be discharged uselessly into the surrounding air.
In such devices steam is introduced into the cooking space and mixes with the air present in the cooking space, thereby partly supplanting this air. The heat of the steam is then transferred to the substance to be cooked, the steam component condensing and being discharged via the discharge tube. Depending on the amount of steam utilized in this process the steam supply is then controlled or regulated with the aid of the sensor depending on the required replenishment. Controlling is effected in that the steam leaves the cooking compartment via the connection tube and is detected by the sensor. When a specific temperature is reached the supply of steam is discontinued but the steam still present in the cooking chamber still gives up heat and condenses. The substantial change in volume during the transition from steam into condensate lowers the pressure in the cooking space, so that cold ambient air is taken in through the measurement-sensor tube. The temperature difference then occuring at the measurement sensor is then used for changing or restoring the steam supply. After a certain predetermined switching temperature has been reached cooling again results in the steam supply being re-connected.
EP-PS 0,171,522 describes a similar device in which the tube is arranged on a side wall or upper wall of the cooking space. In this case the sensor is a device detecting the pressure or the flow rate of the medium flowing through the tube.
The said known constructions have a condensate outlet which constantly discharges condensate, also during the controlled cooking process.